Application of the most popular open CNC system in

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The application of open CNC system in ultra precision machining

after more than 40 years of development, CNC technology has become increasingly mature. In the early 1990s, the concept of open CNC system appeared, and gradually there is a trend that open CNC system replaces the previous special CNC system. At present, all developed countries are competing to develop their own open architecture CNC systems, such as the "next generation workstation/machine tool controller architecture" NGC (the next generationwork station/machine control) of the United States; "Open system architecture for control within Automation Systems" (OSACA) in Europe; open system environment for controller (osec) in Japan, etc. the first item of manufacturing technology in the "guide to key areas of current national priority development of high-tech industrialization" issued by the State Planning Commission and the Ministry of science and technology on July 14, 1999 is "applicable to advanced CNC machine tools and open CNC systems" 。 At present, open CNC system has also been applied in the field of ultra precision machining

1 Characteristics of open CNC system

the current special CNC system (including software and hardware) is basically not portable, and is specially developed for specific machine tools or equipment, which makes its cost very expensive. With the development of manufacturing technology, the whole manufacturing system is required to be more open. We can calculate the relative importance of the keyword and the frequency of the keyword appearing in the document call set, and some contents are more relevant, so as to integrate it into a more flexible system. The concept of open CNC system appeared in the early 1990s. At present, most open CNC systems are based on PC and equipped with various control cards. Compared with the previous special CNC system, the open CNC system generally has the following characteristics:

1) low lattice, high performance price ratio

due to the strong portability of the open CNC system, its development cost is greatly reduced, its maintenance is simpler, its quality is more reliable, and its performance is more perfect, which enhances the market competitiveness of the open CNC system. In the past, there were millions of special ultra precision CNC machining systems, which had the problem of embargo, while the cost of an open ultra precision CNC machining system was much lower

2) modular design

each module in the open CNC system is independent of each other, which allows users to configure the system according to their needs in a large range, such as the number of machine axes, i/o points, etc. when the system hardware is changed, simply modify the CNC system software to meet the needs. It has greater flexibility and can better adapt to the dynamic changes of the market

3) rich and friendly man-machine interface

machine tool manufacturers or users can use different programming languages to develop the most suitable man-machine interface for their own purposes in an open environment, and improve their own CNC system, such as the special control functions of some special machine tools, without too much consideration of the core part of the CNC system controller

4) excellent open performance

whether the open CNC system can overshoot and easily hang the third-party application software, such as various cad/cam software, test software or management software to meet their own needs. The advantage of open CNC system is self-evident

5) support multiple operating platforms

the CNC system with open structure can better support various operating platforms than the previous special CNC system, such as windows, WindowsNT, UNIX, OS2, etc

2 application of open CNC system in ultra precision machining

open CNC system has also been widely used in ultra precision machining because of its own advantages

1) application of foreign open CNC system in ultra precision machining

UK rank pneumo company developed nanoform300 machine tool in the late 1980s. The machine tool can not only cut, but also grind with diamond grinding wheel, and can process aspheric metal mirrors with a diameter of 300mm. The control system of the machine tool adopts the programmable multi axis motion controller (PMAC) of delta tau company in the United States. The controller adopts advanced digital signal processing technology. Motorola's 56001 digital signal processor (DSP) was initially selected. Each card can control up to 8 servo axes, which can be in the form of PC, xt/at, VME, std32 or PCI bus (all can be completely offline). 16/18 bit DAC output resolution. The coding count rate of 10/15mhz is as high as 320mhz effective input bandwidth. The open structure can control any type of motor, with strong processing ability and high flexibility. It is suitable for various bus structures, motor types, feedback components and command data structures in today's practical applications. It is an early successful application of open CNC system in ultra precision machining

rank pneumo's new nanoform250 ultra precision machining system is a two axis ultra precision CNC machine tool that can perform ultra precision turning and grinding. The machine tool can directly grind hard and brittle optical parts with optical surface quality and surface accuracy that can meet the requirements of the optical system. The maximum machining workpiece diameter of the machine tool reaches 250mm. The resolution of the CNC system of the machine tool is 1.25nm. Its CNC system is similar to the nanoform300, and it still adopts the programmable multi axis motion controller of delta tau company in the United States

precitech of the United States, which has a close relationship with the company, has adopted the open CNC system structure on many machine tools it later launched, but its controller is no longer the programmable multi axis motion controller of deltatau of the United States. Instead, adopt the ultrapathtm DSP developed by precitech, and adopt the open CNC system based on precitech's ultrapathtm DSP on the latest machine tools of precitech, such as naonoform200, nan0form350, nanoform600, planoform550, freeform4000, freeform5000, etc. At present, there is little information about the CNC system, but so many machine tools use the same CNC system, which shows that the portability and other performance of the system should be very good

among the three latest machine tools of American Moore company, nanotech500fg, nanotech350upl and nanotechl50ag, except that nanotech500fg uses a special fanucl5i numerical control system with high-speed serial bus. Nanotech350upl and nanotechl50ag adopt open CNC system. Like nanoform300 and nanoform250, nanotech350upl adopts the PMAC controller of delta tau company in the United States, while nanotechl50ag adopts the unidex600 controller of Aerotech company. The controller can control up to 16 servo axes and perform high-speed position locking. The controller uses a RISC processor of up to 33/66MHz. The i960 chip on it can execute several instructions in one clock cycle. The controller integrates a dra1 of up to 32MB, which can peel 3million layers of graphene from a mm thick graphite sheet; It is very hard m and provides powerful processing power. Like other open data systems, it also has strong flexibility and provides rich support software

2) the status of domestic open CNC system and its application in ultra precision machining

in recent years, the domestic research on Open CNC system is also deepening. A large number of university scientific research institutions have developed their own open CNC system, so from the initial design to the production and supply of products. Typical ones are Huazhong type I CNC system of Huazhong University of technology, Zhonghua type I CNC system of Beijing University of Aeronautics and Astronautics, Lantian series high-end CNC system of Shenyang Institute of computing technology, Chinese Academy of Sciences, and five axis five linkage CNC system just launched by Xi'an Jiaotong University at the first China International High Tech achievements fair

however, due to the uniqueness of ultra precision machining, these CNC systems cannot be directly used for ultra precision machining. In the nanosys300 aspheric ultra precision composite machining system being developed in our laboratory, the PMAC controller of delta tau company is selected after demonstration. The following figure is the control system block diagram of the composite machining system

the system adopts PC bus structure. The upper computer is an industrial computer, which communicates with PMAC through the system bus, and can also exchange high-speed data with PMAC through dual port RAM; There is a high-speed DSP on the controller to process the processing data: set the tool with a high-precision LVDT probe; The spindle motor and servo motor are driven by 16 bit DAC, and the closed-loop double position feedback control of the system is realized by high-resolution and high-precision encoder and grating

3 conclusion

it can be predicted that open CNC system will become the mainstream of advanced CNC system in the future with its own advantages, and its application in ultra precision machining will be more extensive. We should seize the time to take measures, invest a lot of human and financial resources in research and development, and promote the development of CNC technology in our country. (end)

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